It is known that polymeric films often have poor handling properties which may result in difficulties in winding the films into high quality reels and inefficient passage through processing, for example, slitting equipment.
Polyester film composites comprising a layer of homo-polyester and a layer of copolyester are described in GB Patent No 1465973. Copolyesters can be used as heat-sealable layers. European Patent No 35835 describes a similar polyester film composite which comprises a filler in the copolyester layer which has an average particle size greater than the thickness of the layer. The filler particles protrude through the copolyester layer yielding a film with food handling properties. However, the aforementioned film can suffer from reduced heat-sealability due to the presence of filler particles which have a particle size greater than the thickness of the heat-sealable layer. In addition, the aforementioned handling property is only achieved at certain heat-sealable layer thickness/filler particle size ratios, such that any variation required in the heat-sealable layer thickness (for example in a different commercial application) necessitates a change in the filler particle size. This situation can result in a range of different fillers being required for different applications. A relatively high concentration of filler may be required in the copolyester layer in order to obtain the required handling properties, which may result in an unacceptable decrease in the optical clarity and an increase in the haze of the film.
We have now developed a composite film which reduces or substantially eliminates at least one or more of the aforementioned problems.